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X-ray Spectroscopy of the Ultra-soft Transient 4U1543-47

Published online by Cambridge University Press:  12 April 2016

H. van der Woerd ,
N.E. White  and
S.M. Kahn
H. van der Woerd
Affiliation:
EXOSAT Observatory, Astrophysics Division, Space Science Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
N.E. White
Affiliation:
EXOSAT Observatory, Astrophysics Division, Space Science Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
S.M. Kahn
Affiliation:
Department of Physics, University of California, Berkeley, CA 94720, U.S.A.

Abstract

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The X-ray transient 4U1543-47 was observed in 1983 by the EXOSAT observatory near the maximum of an outburst. The X-ray spectrum was measured using a gas scintillation proportional counter (GSPC) and a transmission grating spectrometer (TGS). Two emission line features are resolved. A broad (FWHM ~2.7 keV) line at 5.9 keV is detected in the GSPC, which we interprete as a redshifted and broadened iron Kα line. The Une broadening and redshift may arise from either Compton scattering in a cool plasma with small optical depth (τ ≈ 5), or from Doppler and relativistic effects in the vicinity of a compact object. The spectrum below 2 keV, obtained with the TGS, shows evidence for a broad emission line feature at 0.74 keV, which may be an iron L-transition complex. However, we find that such an emission feature could be an artifact caused by an anomalously low interstellar absorption by neutral Oxygen. The continuum emission is extremely soft and is well described by an unsaturated Comptonized spectrum from a very cool plasma (kT = 0.84 keV) with large scattering depth (τ ≈ 27). The continuum spectrum is strikingly similar to that of black hole candidate LMC X-3.

Type
5. Compact Binaries
Information
International Astronomical Union Colloquium , Volume 115: High Resolution X-ray Spectroscopy of Cosmic Plasmas , 1990 , pp. 205 - 208
Copyright
Copyright © Cambridge University Press 1990

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